Conventional endoscopes generally provide only a forward field of view. The field of view angle changes from endoscope to endoscope and can differ from narrow angle to a wide 170° field of view. The geometry of inspected medical and non-medical lumens is usually very complex and it would be useful to have the ability to image over a much wider field of view, and especially to look backwards. Numerous endoscopes provide steering capability where the operator can steer the endoscope tip in order to see and diagnose the surrounding tissue
Unfortunately the lumen traversed is usually narrow and the endoscope tip radius of curvature is larger then the lumen diameter so it is not generally possible with current endoscopes to steer back and look backwards, and if possible, such a maneuver may be painful for the patient and might cause damage to the lumen tissue.
Several solutions have been suggested in the prior art for enhancing the backward view, but there exist a number of drawbacks, such as the need for moving parts which may be difficult to implement in a small endoscope, or which do not deliver the full surround view. Examples of systems for generating views of the internal surfaces of a lumen include the GI-View OmniView camera that is said to deliver a 270° field of view, as described in the article “The Aer-O-Scope: Proof of Concept of a Pneumatic, Skill-Independent, Self-Propelling, Self-Navigating Colonoscope in a Pig Model,” by Pfeffer et al., published in Endoscopy, Vol. 38, pages 105-208 (2006). Another example of such a system is given in International Patent Application Publication No. WO 2006/129977, for “Method and device for simultaneously outputting images of internal front and lateral sides of a pipe”.
Another example is shown in U.S. Pat. No. 4,846,154, which describes two imaging lenses oriented at different angles, and a plate that controls passage or reflection of light through it, controlling from which lens the light is imaged.
The disclosures of each of the publications mentioned in this section and in other sections of the specification are hereby incorporated by reference, each in its entirety.